WO 91/09248 discloses a two part radiator valve assembly for use in closing off a water supply to enable a radiator to be removed. The valve assembly has two mutually opposed valves, each of which comprises a casing in which a through passage is defined, the passages having at contiguous ends internally circumferential valve seats against which respective movable conical valve members are spring biased by respective closing springs, the valve members engaging each other when the valves are placed together to urge the valve members away from the respective valve seats to open the valves. A bayonet coupling sleeve extending between the valve casings to hold the valves together. The casing of the upper of the two valves has an extension accommodating a flow regulating control valve at its distal end, the extension having a branch to be connected to a radiator. Release of the bayonet coupling sleeve allows the valves to separate, automatically closing both valves under the action of the respective closing springs.
A problem with the abovementioned known valve assembly is that the flow rate of liquid through the aligned through passages of the valves causes a resultant force to act on the valve members. At sufficiently high flow rates, such biasing force may be sufficient to displace the valve members from their neutral, mutually open position, against the biasing force of the closing spring of the upstream valve member until the downstream valve member is brought into engagement with its valve seat, closing off flow through the valve assembly.